Fibers in the nanoscale or submicron scale are useful in a variety of applications, including filtration, tissue engineering, protective clothing, composites, battery separators, energy storage, etc. Electrospinning is one of the methods used to generate high quality fibers on this scale. While electrospinning is relatively easy to do, however, it has very low throughput and subsequently, a very high production cost. Therefore, it is not cost effective to electrospin nanoscale and/or submicron scale fibers in large quantities. Accordingly, other than for high-value applications, electrospinning of nanofibers has been largely contained to academic research.
Production rates in current injection nozzle, needle-jet and spinning jet manufacturing processes typically range from about 0.05 grams per hour (g/hr) to about 0.15 g/hr per nozzle/jet. Several methods have been studied and/or used to improve the production rate. These methods include gas-assisted electrospinning; the use of multi-nozzle systems; the use of nozzle-less/needleless systems; and increasing the total number spinning jets. Each of these methods has its problems, however, resulting in maximum sustained production rates of no more than about 2 kilograms per hour (kg/hr) per (commercially available) machine. Problems associated with nozzle/needle systems include: clogging of the injection nozzle/needle orifice; difficulty optimizing the nozzle array; and difficulty maintaining uniform feed rate through each nozzle. Problems associated with nozzle-less/needleless systems include: inability to control solvent evaporation from the solution reservoir, resulting in solution concentration and viscosity variations; and polymer layer coating build-up on the surface of the electrospinning element resulting in a substantial decrease in the fiber spinning rate.
These and other shortcomings are addressed by aspects of the present disclosure.